document.write( "Question 980070: Two trains made the same 150-mile run. Since one train traveled 20 mph faster than the other, it arrived 2 hours earlier. Find the speed of each train. \n" ); document.write( "
Algebra.Com's Answer #601276 by ikleyn(52769)\"\" \"About 
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\n" ); document.write( "\n" ); document.write( "Let  u  be the speed of the faster train in mph (miles per hour).\r
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\n" ); document.write( "\n" ); document.write( "Then the speed of the other train is  u-20 mph.\r
\n" ); document.write( "\n" ); document.write( "We have an equation\r
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\n" ); document.write( "\n" ); document.write( "\"150%2Fu\" - \"150%2F%28u-20%29\" = 2.\r
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\n" ); document.write( "\n" ); document.write( "Solve this equation by simplifying it step by step:\r
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\n" ); document.write( "\n" ); document.write( "\"150%28u-20%29\" - \"150u\" = \"2u%28u-20%29\",\r
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\n" ); document.write( "\n" ); document.write( "\"150u\" - \"3000\" - \"150u\" = \"2u%5E2\" - \"40u\",\r
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\n" ); document.write( "\n" ); document.write( "\"2u%5E2\" - \"40u\" - \"3000\" = \"0\",\r
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\n" ); document.write( "\n" ); document.write( "\"u%5E2\" - \"20u\" - \"1500\" = \"0\". \r
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\n" ); document.write( "\n" ); document.write( "You can solve this quadratic equation by using quadratic formula  (see the lesson  Introduction into Quadratic Equations  in this site). \r
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\n" ); document.write( "\n" ); document.write( "Or,  you can solve it by applying the Viete's formula  (see the lesson  Solving quadratic equations without quadratic formula  in this site). \r
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\n" ); document.write( "\n" ); document.write( "In any case,  the roots of the quadratic equation are  \"u%5B1%5D\" = 50 mph  and  \"u%5B2%5D\" = -30 mph. \r
\n" ); document.write( "\n" ); document.write( "Only positive value of the speed has the sense in this problem,  so that the solution is  u = 50 mph.\r
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\n" ); document.write( "\n" ); document.write( "Answer.  The speed of the faster train is  50 mph.  The speed of the other train is  30 mph. \r
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